Autoclaved aerated concrete is a type of lightweight, precast concrete that is formed under high temperatures and pressures using raw materials such as cement, fine aggregates such as sand or other filler materials, lime, water, and an aerating agent. The aerating agent causes air voids to form in the matrix and increase the porosity of the material, which is accompanied by an increase in the volume of the material along with a reduction in density.
Aerated concrete products offer a number of advantages over conventional concretes including their good strength, low weight, resistance to fire, corrosion, termite and mold, as well as good thermal insulation and sound deadening properties. Due to its lightweight and dimensional accuracy, aerated concretes can be assembled with minimal waste thereby reducing the need for additional equipment in construction and assembling. They offer high durability and require minimum maintenance. The lightweight of aerated concretes also help with lowering shipping costs.
Although favorable when compared to concretes, most conventional aerated concretes are prepared by processes that suffer from a number of deficiencies. The manufacture process of conventional aerated concretes involves special equipment, large energy consumption, and excessive carbon dioxide emission, leaving unfavorable carbon footprint. For example, aerated concretes are typically cured in autoclaves at temperatures ranging from 150° C. to 190° C. and at pressures ranging from 110 psi to 180 psi, to create a stable form of Tobermorite. Tobermorite is the primary binding element in aerated concrete. In addition, they are relatively expensive due to high finishing costs, difficulty to recycling, etc.
There is an on-going need for novel aerated composite materials that match or exceed the physical and performance characteristics of aerated concretes that can be mass-produced at lower cost with improved energy consumption and more desirable carbon footprint.